WinRAR  4.20 Beta 1
# Changes in RAR compression:
* RAR general compression algorithm is optimized for better utilization of several processor cores. While some speed gain is possible even in single processor mode, best results are achieved in multi-core environment.Speed gain depends on data type and average file size. Several cores are utilized more efficiently when compressing large files.
* we had to increase memory requirements to achieve higher compression speed. General RAR compression algorithm allocates about 120 MB comparing to 40 MB in WinRAR 4.11
* RAR text compression algorithm cannot utilize several CPU cores efficiently, so its performance in multiprocessor environment is much lower than for general algorithm. Also its decompression speed is much lower than in general algorithm regardless of CPU number. So we decided to disable the text algorithm by default.If you need maximum possible compression ratio for plain text data regardless of speed, you can enable the text compression in "Advanced compression parameter" dialog. Press "Compression..." button on "Advanced" page of archiving dialog to access it. You can also change this option permanently in default compression profile In the command line mode the text compression can be enabled with -mct switch
* "Fastest" (-m1) compression mode also supports several processor cores now. In 4.11 it could use only a single processor core.
# RAR general decompression algorithm speed is slightly improved, though not to same extent as RAR compression. RAR decompression is not able to use several processor cores, so its performance does not depend on a number of cores.
# Changes in ZIP compression:
* now ZIP compression supports several processor cores resulting in noticeably higher performance in multi-core environment. Single CPU ZIP compression is also faster than in 4.11;
* memory use for ZIP compression is increased to about 15 MB.
# Recovery volume creating and processing can use several CPU cores resulting in higher speed. Though, typically hard drive seek speed is a limiting factor for recovery volumes, so this gain is most noticeable when working with solid state drive.
# Now the allowed value for -mt switch is 1 - 32, not 0 - 16 as before.
# "Find files" command can search data in 7-Zip archives. Previously "Find files" did not support .7z archive format.
# Windows 2000 is not supported by WinRAR and WinRAR self-extracting modules anymore.